There are a number of applications that may need a switching regulator or switched mode power supply to operate in non-inverting buck or boost modes, transitioning relatively seamlessly between the two. Turning to FIG. 1, an example of a bridge 100, which can operate in boost and buck modes can be seen. This bridge 100 is generally an H-bridge, using switches S1 to S4, and an inductor L, which is coupled between the switching nodes of the H-bridge. In buck mode, switches S4 and S3 are closed and open, respectively, while pulse width modulation (PWM) signals are provided to switches S1 and S2. Alternatively, in boost mode, switches S1 and S2 are closed and open, respectively, while PWM signals are provided to switches S3 and S4.
The most inefficient mode of operation, however, is a bridge mode or buck-boost mode, where two of the switches S1 to S4 are closed to generate an inductor voltage VL. Some reasons for the inefficiency are that switching losses are incurred in all four of switches S1 to S4 and that this mode results in a high average inductor current IL. Also contributing to the inefficiency is the rippled current (or variations in the inductor current IL). As can be seen in FIG. 2, switches S1 and S3 are, for example, closed at the same time, and the inductor current IL varies between the periods in which both switches S1 and S3 are close or open, namely between times t1 to t2 and times t3 to t4.
Thus, there is a need for an improved switching regulator.
Some other conventional circuits are: U.S. Pat. No. 6,166,527; U.S. Pat. No. 6,037,755; and U.S. Patent Pre-Grant Publ. No. 2009/0039852.